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December 7: LYRA Flare Observations

  December 7: LYRA Flare observations  
  LYRA Flare observations  


Click on the above image for pdf poster of the above image



A solar flare is an impulsive energy release, seen as a sudden brightening on the Sun. A single solar flare can release as much as 6 × 1025 joules of energy. Solar flares create radiation at wavelengths across the electromagnetic spectrum, from radio waves to gamma rays with a peak in the visible spectral range. Flares often occur in regions of high activity, called active regions, these are seen as bright patches on the face of the Sun in extreme ultraviolet images, such as those taken by the SWAP imager on PROBA2 (see above image). Active regions are formed when magnetic fields generated inside the Sun poke through the surface. The magnetic field lines are traced out by hot plasma trapped upon them. It is believed that Solar flares are caused by the sudden release of magnetic energy through a process called magnetic reconnection, whereby magnetic fields break and reconnect with each other releasing energy and tension.

As mentioned above, solar flares can be seen over a wide spectrum of energies. They are best seen in X-ray and extreme ultraviolet light (EUV). LYRA is a small solar ultraviolet (UV-EUV) radiometer which is designed to observe solar irradiance - the radiative output of the Sun - at a high cadence (> 20 Hz) in four ultraviolet wavelength ranges. The above image shows signatures of several flares recorded by LYRA recorded during four separate periods. The bottom right LYRA curve shows a typical flare signature, with a sudden sharp increase in irradiance followed by a slow decline. The upper left, upper right and lower left curves show signatures of multiple flares occurring one after the other with various strengths.

Lyman-α is the strongest line in the solar spectrum and is of particular importance for its impact on the Earth atmosphere, a paper discussing observations of Lyman-α flares made with LYRA can be found here.